NOAA sees sea level rise of up to 6.6 feet by 2100

Dec. 6, 2012
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Global sea levels will likely rise between 8 inches (0.2 meters) and 6.6 feet (2.0 meters) by the end of this year, depending on four scenaria that look at different amounts of ice sheet loss and ocean warming, according to a report Dec. 6 by the National Oceanic and Atmospheric Administration. / National Oceanic and Atmospheric Administration

by Wendy Koch, USA TODAY

by Wendy Koch, USA TODAY

As recovery continues from Superstorm Sandy, the U.S. government reports Thursday that flooding from future storms will likely worsen as global sea levels rise between 8 inches and 6.6 feet by the end of this century.

The National Oceanic and Atmospheric Administration's latest assessment, similar to others in recent years, also says higher sea levels -- regardless of the extent of global warming -- won't stop in 2100. It says 8 million people live in U.S. coastal areas at risk of flooding and many of the nation's military, energy and commercial assets are located at or near the ocean.

Despite uncertainty about the extent of sea level rise, "what we do know is that higher mean sea levels will increase the frequency, magnitude and duration of flooding" from storms, says co-author and NOAA scientist Adam Parris. He says the biggest uncertainty is the amount of water that will come from melting glaciers in Greenland and Antarctica.

In the United States, NOAA finds the U.S. Gulf Coast and Chesapeake Bay will continue to experience the most rapid and highest amounts of sea level rise, because some of the land there is subsiding. It says parts of Alaska and the Pacific Northwest, where land is rising, may experience much less or no sea level change.

The report by NOAA's Climate Program Office, based on the latest scientific research and compiled by government and academic scientists, looks at four different scenarios for future change. It sees a greater than 90% chance that global mean sea level will rise at least 8 inches (0.2 meters) but less than 6.6 feet (2.0 meters), depending on ice sheet loss and ocean warming.

Scientists largely agree that sea levels worldwide are now about a foot higher than a century ago, because seawater expands in warmer oceans. The 2007 Intergovernmental Panel on Climate Change said sea levels will rise at least 2 feet this century, but NASA climate scientist James Hansen and Stanford's Ken Caldeira reported last year that sea level could rise more than 3 feet by 2100 because of ice sheet melting not accounted for in the 2007 report.

In June, the U.S. Geological Survey reported in the journal Nature Climate Change that sea level rise along the U.S. Atlantic Coast has been climbing at a rate three to four times higher than the global average since 1950 -- now about 1.5 inches per decade.

NOAA's report, designed to help U.S. policymakers assess the risks associated with sea level rise, was prepared by scientists at its agency as well as those from NASA, the U.S. Geological Survey, the Scripps Institution of Oceanography, the U.S. Department of Defense, the U.S. Army Corps of Engineers, Columbia University, the University of Maryland, the University of Florida and the South Florida Water Management District.